U.S. patent application number 14/366028 was filed with the patent office on 2015-11-12 for capacitor.
This patent application is currently assigned to NICHICON CORPORATION. The applicant listed for this patent is Naoya MARUYAMA, Mitsuru YONEDA. Invention is credited to Naoya MARUYAMA, Mitsuru YONEDA.
Application Number | 20150325383 14/366028 |
Document ID | / |
Family ID | 48697178 |
Filed Date | 2015-11-12 |
United States Patent
Application |
20150325383 |
Kind Code |
A1 |
YONEDA; Mitsuru ; et
al. |
November 12, 2015 |
CAPACITOR
Abstract
The present application provides a capacitor in which the
operability of the pressure valve, and valve deformation during
operation, can be stabilized. A capacitor (1) comprising: a
capacitor element (6) obtained by overlapping and winding a
positive electrode foil (8) and a negative electrode foil (7) with
an electrolytic paper (3) interposed therebetween, and impregnating
the foils with an electrolytic solution; a bottomed cylindrical
outer case (4) for housing the capacitor element (6); and a sealing
body (2) for sealing the opening of the outer case (4). The inner
bottom part of the outer case (4) has formed thereon a recess (21)
having: a first inclined surface (22) spreading in a radial manner
from the center region of the inner bottom part, the center region
being the deepest part; and a second inclined surface (23) which is
continuous from the outer edge of the first inclined surface (22)
and which is steeper than the first inclined surface (22). A
weakened section is formed in the recess, and a groove is formed on
the outside of the inner bottom part of the outer case.
Inventors: |
YONEDA; Mitsuru; (Kyoto-shi,
JP) ; MARUYAMA; Naoya; (Kyoto-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
YONEDA; Mitsuru
MARUYAMA; Naoya |
Kyoto-shi
Kyoto-shi |
|
JP
JP |
|
|
Assignee: |
NICHICON CORPORATION
Kyoto-shi
JP
|
Family ID: |
48697178 |
Appl. No.: |
14/366028 |
Filed: |
December 18, 2012 |
PCT Filed: |
December 18, 2012 |
PCT NO: |
PCT/JP2012/082721 |
371 Date: |
June 17, 2014 |
Current U.S.
Class: |
361/512 |
Current CPC
Class: |
H01G 9/048 20130101;
H01G 11/26 20130101; H01G 9/12 20130101; H01G 11/80 20130101; H01G
11/14 20130101; H01G 11/58 20130101; H01G 11/52 20130101; H01G
9/145 20130101; H01G 11/18 20130101; H01G 9/10 20130101; Y02E 60/13
20130101; H01G 11/78 20130101; H01G 9/035 20130101; H01G 11/82
20130101 |
International
Class: |
H01G 11/14 20060101
H01G011/14; H01G 11/58 20060101 H01G011/58; H01G 11/52 20060101
H01G011/52; H01G 9/035 20060101 H01G009/035; H01G 11/26 20060101
H01G011/26; H01G 9/048 20060101 H01G009/048; H01G 9/10 20060101
H01G009/10; H01G 9/12 20060101 H01G009/12; H01G 9/145 20060101
H01G009/145; H01G 11/80 20060101 H01G011/80 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2011 |
JP |
2011-287023 |
Claims
1. A capacitor comprising: a capacitor element being formed by
overlaying and winding a anode foil and a cathode foil with a
separator interposed between the anode foil and the cathode foil
and by being impregnated with an electrolytic solution; an exterior
case for housing the capacitor element, the exterior case having a
cylindrical shape with a bottom; and an opening sealing body for
sealing an opening of the exterior case, a recessed part being
formed on an inner bottom of the exterior case, the recessed part
having: a first inclined surface radially expanding from a central
part area of the inner bottom, the central part area of the inner
bottom being the deepest portion of the inner bottom; and a second
inclined surface continuing to an outer edge of the first inclined
surface, the second inclined surface being steeper than the first
inclined surface, a weak portion being formed inside of the
recessed part, a groove part being formed outside of the inner
bottom of the exterior case, a thick-wall portion being formed on a
periphery of the recessed part, an outer edge portion of a surface
of the capacitor element being in contact with the thick-wall
portion, the surface facing the inner bottom of the exterior
case.
2. The capacitor according to claim 1, wherein in the deepest
portion, a flat part having a diameter within a range of 3% to 28%
of an internal diameter of the exterior case is provided.
3. The capacitor according to claim 1, wherein an inclination angle
of the first inclined surface is an angle within a range of
0.5.degree. to 2.0.degree. with respect to a horizontal plane on
which the inner bottom is arranged.
4. The capacitor according to claim 1, wherein a length of an edge
portion of the inner bottom of the exterior case is a length within
a range of 11% to 29% of a diameter of the exterior case.
5. The capacitor according to claim 1, wherein a thickness of a
thick-wall portion of the inner bottom of the exterior case is a
thickness within a range of 0.5 mm to 1.0 mm.
6. The capacitor according to claim 1, wherein the surface of the
thick-wall portion being in contact with the capacitor element is
flat.
7. The capacitor according to claim 2, wherein an inclination angle
of the first inclined surface is an angle within a range of
0.5.degree. to 2.0.degree. with respect to a horizontal plane on
which the inner bottom is arranged.
8. The capacitor according to claim 7, wherein a length of an edge
portion of the inner bottom of the exterior case is a length within
a range of 11% to 29% of a diameter of the exterior case.
9. The capacitor according to claim 8, wherein a thickness of a
thick-wall portion of the inner bottom of the exterior case is a
thickness within a range of 0.5 mm to 1.0 mm.
10. The capacitor according to claim 7, wherein a thickness of a
thick-wall portion of the inner bottom of the exterior case is a
thickness within a range of 0.5 mm to 1.0 mm.
11. The capacitor according to claim 2, wherein a length of an edge
portion of the inner bottom of the exterior case is a length within
a range of 11% to 29% of a diameter of the exterior case.
12. The capacitor according to claim 11, wherein a thickness of a
thick-wall portion of the inner bottom of the exterior case is a
thickness within a range of 0.5 mm to 1.0 mm.
13. The capacitor according to claim 2, wherein a thickness of a
thick-wall portion of the inner bottom of the exterior case is a
thickness within a range of 0.5 mm to 1.0 mm.
14. The capacitor according to claim 3, wherein a length of an edge
portion of the inner bottom of the exterior case is a length within
a range of 11% to 29% of a diameter of the exterior case.
15. The capacitor according to claim 14, wherein a thickness of a
thick-wall portion of the inner bottom of the exterior case is a
thickness within a range of 0.5 mm to 1.0 mm.
16. The capacitor according to claim 3, wherein a thickness of a
thick-wall portion of the inner bottom of the exterior case is a
thickness within a range of 0.5 mm to 1.0 mm.
17. The capacitor according to claim 4, wherein a thickness of a
thick-wall portion of the inner bottom of the exterior case is a
thickness within a range of 0.5 mm to 1.0 mm.
Description
TECHNICAL FIELD
[0001] The present invention relates to a capacitor and, more
particularly, to a capacitor which contains an electrolytic
solution inside of its exterior case.
BACKGROUND ART
[0002] As a capacitor which contains an electrolytic solution
inside of its exterior case, there are an electrolytic capacitor
and an electric double-layer capacitor.
[0003] In the electrolytic capacitor, metal referred to as a valve
metal such as aluminum, tantalum and niobium is used for its
electrodes, an anode of the electrodes is oxidized, and the
resultant which is an oxide film layer is used as a dielectric.
[0004] In the electric double-layer capacitor, a phenomenon (an
electric double-layer) in which charges are arrayed at extremely
short distances in interfaces between electrodes (polarized
electrodes) and an electrolytic solution is utilized.
[0005] In a method of manufacturing an aluminum electrolytic
capacitor in which aluminum is used for its electrodes, etching
processing and oxide film formation processing are performed, an
anode foil and a cathode foil to which electrode lead-out terminals
are respectively attached are wound via separators, and the
resultant is fixed by an element stopper tape, thereby forming a
capacitor element. This capacitor element is impregnated with an
electrolytic solution for driving and thereafter, is housed in an
exterior case having a cylindrical shape with a bottom. There may
be a case where the capacitor element is fixed inside of the case
by using a fixation material.
[0006] Further, an opening sealing body is attached to an opening
of the exterior case, and the opening has a configuration which is
sealed through drawing processing.
[0007] In an aluminum electrolytic capacitor whose terminal shape
is substrate-self-supporting-type, a positive electrode terminal
and a negative electrode terminal are formed on an external end
face of the opening sealing body, and a positive electrode tab
terminal and a negative electrode tab terminal led out from the
capacitor element are electrically connected to end portions of
these terminals. In addition, in an aluminum electrolytic capacitor
whose terminal shape is lead-wire type, lead terminals electrically
connected to a positive electrode tab terminal and a negative
electrode tab terminal which are led out from a capacitor element
are led out externally through an insertion hole provided in an
opening sealing body.
[0008] A capacitor element of the electric double-layer capacitor
in which polarized electrode layers are formed on current
collectors formed of a metal foil such as an aluminum foil is
obtained by winding an anode foil and a cathode foil to which
electrode lead-out terminals are attached via separators. In the
electric double-layer capacitor, the capacitor element mentioned
above is impregnated with an electrolytic solution and is housed in
a case formed of aluminum or the like and having a cylindrical
shape with a bottom. As described above, the electric double-layer
capacitor and the aluminum electrolytic capacitor are different
from each other only in configurations of the electrodes and have
the same configurations.
[0009] When an abnormal stress such as an overvoltage and an
excessive ripple current is applied to each of the above-described
capacitors containing the electrolytic solution thereinside, the
electrolytic solution is decomposed and a gas is generated. When
this generation of the gas increases an internal pressure of the
capacitor, the capacitor is ruptured. Therefore, a weak portion is
provided at a bottom portion of the exterior case having the
cylindrical shape with the bottom and is caused to function as a
safety device (pressure valve) operating in accordance with an
increase in the internal pressure to release the internal pressure
externally.
[0010] A pressure at which this pressure valve operates can be set
to a desired pressure by adjusting a thickness of the weak portion.
However, the higher the pressure at which the pressure valve
operates is, the larger a range in which the valve is opened is,
thereby leading to a problem in that the bottom portion of the
exterior case after opening the valve is largely deformed.
Therefore, there proposed is the technology in which a thick-wall
portion formed so as to be thicker than a side wall portion is
formed in a bottom of the exterior case, a thin-wall portion is
formed within a range of this thick-wall portion, and linear
grooves serving as the weak portion are further formed in the
thin-wall portion, thereby limiting to the thin-wall portion the
range in which the valve is opened (refer to Patent Literature
1).
PRIOR ART LITERATURE PATENT LITERATURE
[0011] Patent Literature 1: JP2001-307967A
SUMMARY OF THE INVENTION
Technical Problem
[0012] However, in the conventional safety device, since the weak
portion, formed inside of the bottom of the exterior case, and an
inside of the case of the thin-wall portion are formed
substantially in parallel with each other, a pressure exerted in
accordance with an increase in the internal pressure is applied to
the whole of the weak portion and the thin-wall portion is also
largely deformed. Therefore, in view of devising of a reduction in
a height of the deformation of the bottom of the exterior case, the
conventional safety device is still insufficient.
[0013] In order to solve the above-described problem, the present
invention was made. An object of the present invention is to
provide a capacitor capable of stabilizing operativeness of a
pressure valve and the deformation of the pressure valve upon the
operation.
Solution to Problem
[0014] The present invention relates to a capacitor which includes:
a capacitor element being formed by overlaying and winding a anode
foil and a cathode foil with a separator interposed between the
anode foil and the cathode foil and by being impregnated with an
electrolytic solution; an exterior case for housing the capacitor
element, the exterior case having a cylindrical shape with a
bottom; and an opening sealing body for sealing an opening of the
exterior case. In the capacitor, a recessed part is formed on an
inner bottom of the exterior case, the recessed part having: a
first inclined surface radially expanding from a central part area
of the inner bottom, the central part area of the inner bottom
being the deepest portion of the inner bottom; and a second
inclined surface continuing to an outer edge of the first inclined
surface, the second inclined surface being steeper than the first
inclined surface, a weak portion is formed inside of the recessed
part, and a groove part is formed outside of the inner bottom of
the exterior case.
[0015] By employing this configuration, the recessed part
constituted of the first inclined surface and the second inclined
surface is provided in the inner bottom of the exterior case,
thereby allowing a starting point of the deformation of the bottom
of the exterior case caused in accordance with an increase in an
internal pressure of the exterior case to be set only in the
recessed part, instead of being in the whole of the inner bottom.
Thus, upon deforming the bottom in accordance with the increase in
the internal pressure, an amount of deformation of the bottom can
be suppressed and a height of deformation can be reduced. In
addition, the starting point of the deformation is set only in the
recessed part, thereby allowing the deformation at a desired
internal pressure to be stabilized.
[0016] In addition, in the capacitor of the present invention, in
the deepest portion, a flat part having a diameter within a range
of 3% to 28% of an internal diameter of the exterior case is
provided.
[0017] In addition, in the capacitor of the present invention, an
inclination angle of the first inclined surface is an angle within
a range of 0.5.degree. to 2.0.degree. with respect to a horizontal
plane on which the inner bottom is arranged.
[0018] In addition, in the capacitor of the present invention, a
length of an edge portion of the inner bottom of the exterior case
is a length within a range of 11% to 29% of a diameter of the
exterior case.
[0019] In addition, in the capacitor of the present invention, a
thickness of a thick-wall portion of the inner bottom of the
exterior case is a thickness within a range of 0.5 mm to 1.0
mm.
[0020] By employing the above-described configuration, variation in
a working pressure and an amount of deformation can be reduced.
Advantageous Effects of the Invention
[0021] According to the present invention, a capacitor is capable
of stabilizing operativeness of a pressure valve and the
deformation of the pressure valve upon the operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 (a) is a perspective view illustrating a
configuration of a capacitor according to the present invention and
FIG. 1 (b) is a partial cross-sectional view illustrating the
configuration of the capacitor according to the present
invention.
[0023] FIG. 2 (a) is a plan view showing the configuration of the
capacitor according to the present invention and FIG. 2 (b) is an
enlarged cross-sectional view illustrating the configuration of the
capacitor according to the present invention.
[0024] FIG. 3 is a cross-sectional view illustrating a state of the
capacitor according to the present invention before operating a
valve.
[0025] FIG. 4 is a cross-sectional view illustrating a state of the
capacitor according to the present invention after operating the
valve.
[0026] FIG. 5 is a cross-sectional view illustrating a state of the
conventional capacitor before operating a valve.
[0027] FIG. 6 is a cross-sectional view illustrating a state of the
conventional capacitor after operating the valve.
[0028] FIG. 7 is an enlarged cross-sectional view showing a
configuration of a recessed part in another embodiment of the
present invention.
[0029] FIG. 8 (a), FIG. 8 (b), and FIG. 8 (c) are plan views each
showing a configuration of a groove part in another embodiment of
the present invention.
DESCRIPTION OF EMBODIMENTS
[0030] Hereinafter, an embodiment of the present invention will be
described with reference to the accompanying drawings.
[0031] As shown in FIG. 1 (a) and FIG. 1 (b), in a capacitor 1
according to the present embodiment, a capacitor element 6 is
configured such that an anode foil 8 and a cathode foil 7 which are
formed of a valve metal are overlaid and wound with electrolytic
papers 9 as separators interposed therebetween and a winding
stopper tape 5 is attached at an winding end portion. Further, this
capacitor element 6 is impregnated with an electrolytic solution
for driving not shown.
[0032] A metal case 4 which is an exterior case is a metal case
which has a cylindrical shape with a bottom and is to house the
above-mentioned capacitor element 6. An opening sealing terminal
plate 2 which is an opening sealing body includes a pair of
terminals 11 to which lead tabs 3 for external leading-out, led out
from the above-described capacitor element 6, are connected.
[0033] The opening sealing terminal plate 2 is provided in an
opening of the metal case 4 by curling an open end of the metal
case 4 for tight sealing and is configured to thereby ensure
airtightness of the capacitor.
[0034] As shown in FIG. 2 (a) and FIG. 2 (b), on a bottom of the
metal case 4, a pressure valve 20 is provided. The pressure valve
20 is constituted of: a recessed part 21 which is formed on an
inner bottom of the metal case 4 and has a circular-shaped planar
view; and a cruciform groove part 31 which is formed on an external
face side of the bottom of the metal case 4.
[0035] As shown in FIG. 2 (a), the recessed part 21 is formed in a
recessed manner on the inner bottom of the metal case 4 so as to
have the substantially circular-shaped planer view having a
predetermined diameter. As shown in FIG. 2 (b), the recessed part
21 is formed by an inclined surface having two inflection points P1
and P2 on a periphery thereof. Specifically, on the inner bottom of
the metal case 4, the recessed part 21 is formed by a first
inclined surface 22 radially expanding from the flat part 24 having
the substantially circular-shaped planar view, formed in a central
part area (the deepest portion of the inner bottom) and a second
inclined surface 23 continuing to an outer edge of the first
inclined surface 22. The first inflection point P1 forms an outer
edge of the first inclined surface 22 and constitutes a boundary
between a gentle inclination of the first inclined surface 22 and a
steeper inclination of the second inclined surface 23 than the
gentle inclination of the first inclined surface 22. The second
inflection points P2 constitutes an outer edge of the second
inclined surface 23. A step part constituted of the steep second
inclined surface 23 is formed by the first inflection points P1 and
the second inflection points P2.
[0036] In the present invention, the first inclined surface 22 is
not limited to a flat surface and may be an inclined surface having
a curved surface whose degree of the inclination becomes gentle
gradually from the first inflection point P1 toward the central
part area (flat part 24) of the inner bottom.
[0037] A diameter of the flat part 24 provided in the central part
area of the inner bottom is in a range of 3% to 28% of an internal
diameter of the metal case 4.
[0038] By setting the diameter to be in the range of 3 to 28%, in
addition to the effects attained by the configuration including the
recessed part 21 which has the weak portion thereinside (effects
that an amount of deformation of the bottom of the metal case 4
caused by an increase in the internal pressure of the metal case 4
can be suppressed and that a height of the deformation can be
reduced), effects that the variation in a working pressure and an
amount of deformation can be reduced and that a sufficient length
of the second inclined surface 23 which is an important factor in
the present invention can be obtained can be attained.
[0039] In addition, an inclination angle of the first inclined
surface 22 with respect to a horizontal plane (horizontal plane on
which the inner bottom is arranged) in FIG. 2 (b), which is in a
range of 0.5.degree. to 2.0.degree., is appropriate. By setting the
inclination angle thereof to be in the range of 0.5.degree. to
2.0.degree., a sufficient angle of the first inclined surface 22
which is an important factor in the present invention can be
obtained. Furthermore, in addition to the effects attained by the
configuration including the recessed part 21 which has the weak
portion thereinside (effects that the amount of deformation of the
bottom of the metal case 4 caused by the increase in the internal
pressure of the metal case 4 can be suppressed and that the height
of the deformation can be reduced), the effect that the variation
in the working pressure and the amount of deformation can be
reduced can be attained.
[0040] In addition, a length L11 of an edge portion of the inner
bottom of the metal case 4 which is in a range of 11% to 29% of a
diameter of the metal case 4 is appropriate. By setting the length
L11 to be in the range of 11% to 29%, since a sufficient length of
the thick-wall portion of the bottom can be ensured, an effect to
suppress the expansion of the valve can be attained. Furthermore,
in addition to the effects attained by the configuration including
the recessed part 21 which has the weak portion thereinside
(effects that the amount of deformation of the bottom of the metal
case 4 caused by the increase in the internal pressure of the metal
case 4 can be suppressed and that the height of the deformation can
be reduced), the effect that the variation in the working pressure
and the amount of deformation can be reduced can be attained.
[0041] In addition, regardless of a size of the metal case 4, a
thickness T11 of the thick-wall portion of the inner bottom of the
metal case 4 which is in a range of 0.5 mm to 1.0 mm is
appropriate. By setting the thickness T11 to be in the range of 0.5
mm to 1.0 mm, since a sufficient thickness of the thick-wall
portion of the bottom can be ensured, the effect to suppress the
expansion of the valve can be attained. Furthermore, in addition to
the effects attained by the configuration including the recessed
part 21 which has the weak portion thereinside (effects that the
amount of deformation of the bottom of the metal case 4 caused by
the increase in the internal pressure of the metal case 4 can be
suppressed and that the height of the deformation can be reduced),
the effect that the variation in the working pressure and the
amount of deformation can be reduced can be attained.
[0042] As described above, in the present embodiment, as the
recessed part 21 of the pressure valve 20, the configuration having
the steeply inclined surface (steep second inclined surface 23
having the step portion) and the gently inclined surface (first
inclined surface 22) expanding toward the central part area of the
inner bottom is employed (FIG. 3). Thus, a starting point of the
deformation of the bottom of the metal case 4 caused in accordance
with the increase in the internal pressure of the metal case 4 can
be set to be only in the recessed part 21, instead of being in the
whole of the inner bottom, thereby allowing a deformation state to
be controlled so as to be substantially constant (FIG. 4).
[0043] In this respect, in the conventional capacitor 100 (FIG. 5),
in a bottom of a metal case 4, the recessed part 21 having the two
inclined surfaces (the first inclined surface 22 and the second
inclined surface 23) as in the present embodiment is not provided.
Therefore, a starting point of the deformation of the metal case 4
caused in accordance with the increase in the internal pressure of
the metal case 4 is set to be in the whole of the bottom (FIG. 6),
thereby leading to a problem in that a height of the deformation of
the bottom is increased. However, in the capacitor 1 (FIG. 3 and
FIG. 4) according to the present embodiment, this problem is
remedied and the amount of deformation upon opening the pressure
valve 20 is suppressed, thereby allowing the height of the
deformation to be reduced.
[0044] In addition, the starting point of the deformation can be
set to be only in the recessed part 21, thereby allowing
operativeness at a desired valve working pressure to be
stabilized.
[0045] In the above-described embodiment, as shown in FIG. 2 (a)
and FIG. 2 (b), the case where the recessed part 21 having the one
step portion with the steep second inclined surface 23 is formed in
the inner bottom of the metal case 4 is described. However, the
present invention is not limited thereto. For example, as shown in
FIG. 7, another steep inclined surface 26 may be additionally
formed and a recessed part having two-step portion with the
inclined surface 23 and the 26 may be configured. Furthermore, the
number of steps is not limited thereto and may be three or
more.
[0046] In addition, the above-described embodiment, the case where
the cruciform groove part 31 is formed is described. However, the
present invention is not limited thereto. For example, as shown in
FIG. 8(a), FIG. 8(b), and FIG. 8(c), it is only required for the
weak portion to be disposed in the substantially central portion of
the bottom of the metal case 4, and a groove part 31 having each of
a variety of shapes may be adopted.
Examples
[0047] Hereinafter, with reference to examples, the present
invention will be further specifically described.
[0048] First, with respect to the metal case 4 (one-step shape
shown in FIG. 2 (a) and FIG. 2 (b)) and the metal case 4 having the
recessed part with the two-step shape shown in FIG. 7, which are
described in the above embodiment, and the metal case having the
conventional shape with no recessed part 21 being formed, a
hydraulic test was conducted.
[0049] In the hydraulic test, with respect to a metal case of each
of an example shape (example (one-step)) in which the pressure
valve 20 having the groove part 31 and the recessed part 21 with
the one-step shape (FIG. 2 (a) and FIG. 2 (b)) is provided, an
example shape (example (two-step)) in which the pressure valve 20
having the groove part 31 and the recessed part 21 with the
two-step shape (FIG. 7) is provided, and the conventional shape
(conventional example) in which the pressure valve constituted of
only the groove part 31 is provided, a working pressure and a
height of the deformation upon the operation (upon the opening) of
each of the pressure valves were measured. A result of the
measurement is shown in Table 1.
TABLE-US-00001 TABLE 1 Working pressure Height of deformation
(kgf/cm.sup.2) (mm) Conventional example 9.5 1.92 Example
(one-step) 9.5 1.26 Example (two-step) 9.5 1.23
[0050] The following is seen from Table 1. In the metal case 4
according to each of the embodiments of the present invention, as
compared with that of the conventional shape, it was made possible
to suppress the height of deformation of the bottom of the metal
case 4 related to the abrupt deformation caused by the hydraulic
pressure while the valve working pressure was the same as that of
the conventional shape.
[0051] Next, with respect to the metal case 4 (one-step shape shown
in FIG. 2 (a) and FIG. 2 (b)) and the metal case 4 having the
recessed part with the two-step shape shown in FIG. 7, which are
described in the above embodiment and the metal case having the
conventional shape with no recessed part 21 being formed, a
reliability test was conducted.
[0052] In the reliability test, with respect to a metal case of
each of an example shape (example (one-step)) in which the pressure
valve 20 having the groove part 31 and the recessed part 21 with
the one-step shape (FIG. 2 (a) and FIG. 2 (b)) is provided, an
example shape (example (two-step)) in which the pressure valve 20
having the groove part 31 and the recessed part 21 with the
two-step shape (FIG. 7) is provided, and the conventional shape
(conventional example) in which the pressure valve constituted of
only the groove part 31 is provided, the reliability test by the
application of a ripple current was conducted for 2000 hours and a
height of deformation of each of the pressure valves was measured.
A result of the measurement is shown in Table 2.
TABLE-US-00002 TABLE 2 Height of deformation (mm) Conventional
example 2.03 Example (one-step) 1.15 Example (two-step) 1.22
[0053] The following is seen from Table 2. In the metal case 4
according to each of the embodiments of the present invention, as
compared with that of the conventional shape, it was made possible
to suppress the height of deformation of the bottom of the metal
case 4 related to the gradual deformation caused by the long-term
reliability test while the valve working pressure was the same as
that of the conventional shape.
[0054] Next, with respect to a case where a diameter of the flat
part 24 (FIG. 2 (b)) provided in the central part area of the inner
bottom of the metal case 4 is 10% of the internal diameter of the
metal case 4, which is within the range of 3% to 28%, a case where
a diameter of the flat part 24 (FIG. 2 (b)) provided in the central
part area of the inner bottom of the metal case 4 is 1% of the
internal diameter of the metal case 4, which is out of the range of
3% to 28%, and a case where a diameter of the flat part 24 (FIG. 2
(b)) provided in the central part area of the inner bottom of the
metal case 4 is 35% of the internal diameter of the metal case 4,
which is out of the range of 3% to 28%, a working pressure of each
of the pressure valves and a height of deformation of each of the
pressure valves upon the measurement result was obtained. A result
of the measurement is shown in Table 3.
TABLE-US-00003 TABLE 3 Ratio of a diameter of a flat Variation
(Standard deviation) part to an internal diameter of Working
Deformation a metal case (%) pressure amount Example 1 1.89 1.97
Example 10 0.82 0.92 Example 35 2.14 2.55
[0055] The following is seen from Table 3. In the case where the
diameter of the flat part 24 (FIG. 2 (b)) provided in the central
part area of the inner bottom of the metal case 4 was 10% of the
internal diameter of the metal case 4 which was within the range of
3% to 28%, as compared with the cases where the diameters of the
flat parts 24 (FIG. 2 (b)) provided in the central part areas of
the inner bottoms of the metal cases 4 were out of the range of 3%
to 28%, it was made possible to reduce the variation in the working
pressure and the amount of deformation.
[0056] Next, with respect to a case where an inclination angle of
the first inclined surface 22 with respect to a horizontal plane in
FIG. 2 (b) is 1.0.degree., which is in a range of 0.5.degree. to
2.0.degree., a case where an inclination angle of the first
inclined surface 22 with respect to the horizontal plane in FIG. 2
(b) is 0.1.degree., which is out of the range of 0.5.degree. to
2.0.degree., and a case where an inclination angle of the first
inclined surface 22 with respect to the horizontal plane in FIG. 2
(b) is 3.0.degree., which is out of the range of 0.5.degree. to
2.0.degree., a working pressure of each of the pressure valves and
a height of deformation of each of the pressure valves upon the
operation (upon the opening) were measured and a standard deviation
of the measurement result was obtained. A result of the measurement
is shown in Table 4.
TABLE-US-00004 TABLE 4 Inclination angle of a first inclined
surface with respect Variation (Standard deviation) to a horizontal
plane of a Working Deformation metal case (.degree.) pressure
amount Example 0.1 1.59 1.57 Example 1.0 0.92 0.93 Example 3.0 1.54
1.77
[0057] The following is seen from Table 4. In the case where the
inclination angle of the first inclined surface 22 with respect to
the horizontal plane in FIG. 2 (b) was 1.0.degree., which is in the
range of 0.5.degree. to 2.0.degree., as compared with the cases
where the inclination angles of the first inclined surfaces 22 with
respect to the horizontal plane in FIG. 2 (b) were out of the range
of 0.5.degree. to 2.0.degree., it was made possible to reduce the
variation in the working pressure and the amount of
deformation.
[0058] Next, with respect to a case where a length L11 (FIG. 2 (b))
of an edge portion of the inner bottom of the metal case 4 accounts
for 20% of a diameter of the metal case 4, which is in a range of
11% to 29%, a case where the length L11 (FIG. 2 (b)) of the edge
portion of the inner bottom of the metal case 4 accounts for 5% of
the diameter of the metal case 4, which is out of the range of 11%
to 29%, and a case where the length L11 (FIG. 2 (b)) of the edge
portion of the inner bottom of the metal case 4 accounts for 35% of
the diameter of the metal case 4, which is out of the range of 11%
to 29%, a working pressure of the pressure valve and a height of
deformation upon the operation (upon the opening) were measured and
a standard deviation of the measurement result was obtained. A
result of the measurement is shown in Table 5.
TABLE-US-00005 TABLE 5 Ratio of a length of an edge portion of an
inner bottom Variation (Standard deviation) of a metal case to a
diam- Working Deformation eter of the metal case (%) pressure
amount Example 5 1.69 1.87 Example 20 0.85 0.91 Example 35 1.83
1.87
[0059] The following is seen from Table 5. In the case where the
length L11 (FIG. 2 (b)) of the edge portion of the inner bottom of
the metal case 4 accounts for 20% of the diameter of the metal case
4, which is within the range of 11% to 29%, as compared with the
cases where the lengths L11 (FIG. 2 (b)) of the edge portions of
the inner bottoms of the metal cases 4 account for the percentages,
which are out of the range of 11% to 29%, it was made possible to
reduce the variation in the working pressure and the amount of
deformation.
[0060] Next, with respect to a case where regardless of a size of
the metal case 4, a thickness T11 of a thick-wall portion of the
inner bottom of the metal case 4 is 0.7 mm, which is in a range of
0.5 mm to 1.0 mm, a case where regardless of the size of the metal
case 4, a thickness T11 of the thick-wall portion of the inner
bottom of the metal case 4 is 0.2 mm, which is out of the range of
0.5 mm to 1.0 mm, and a case where regardless of the size of the
metal case 4, a thickness T11 of the thick-wall portion of the
inner bottom of the metal case 4 is 1.5 mm, which is out of the
range of 0.5 mm to 1.0 mm, a working pressure of the pressure valve
and a height of deformation upon the operation (upon the opening)
were measured and a standard deviation of the measurement result
was obtained. A result of the measurement is shown in Table 6.
TABLE-US-00006 TABLE 6 Thickness of a thick-wall Variation
(Standard deviation) portion of an inner bottom Working Deformation
of a metal case (mm) pressure amount Example 0.2 1.77 1.81 Example
0.7 0.88 0.95 Example 1.5 1.91 1.93
[0061] The following is seen from Table 6. In the case where
regardless of the size of the metal case 4, the thickness T11 of
the thick-wall portion of the inner bottom of the metal case 4 is
0.7 mm which is in the range of 0.5 mm to 1.0 mm, as compared with
the cases where thicknesses T11 of the thick-wall portions of the
inner bottoms of the metal cases 4 are out of the range of 0.5 mm
to 1.0 mm, it was made possible to reduce the variation in the
working pressure and the amount of deformation.
[0062] In the above-described embodiment, the description related
to the electrolytic capacitor is given. However, needless to say,
even when the present invention is used for an exterior case of an
electric double-layer capacitor, the same effects can be
attained.
[0063] In addition, in the above-described embodiment, the
description related to the case where the recessed part having the
step portion of the one-step with the steep second inclined surface
is formed in the inner bottom of the metal case is given. However,
for example, by additionally forming a steeply inclined surface, a
recessed part having a two-step shape may be configured. Further,
the number of steps is not limited thereto and may be three or
more.
[0064] Furthermore, in the above-described embodiment, the
description related to the case where the cruciform groove part is
formed is given. However, for example, it is only required for the
weak portion to be disposed in the substantially central portion of
the bottom of the metal case, and a groove part having each of a
variety of shapes may be adopted.
REFERENCE SIGNS LIST
[0065] 1 capacitor [0066] 2 opening sealing terminal plate (opening
sealing body) [0067] 3 lead tab [0068] 4 metal case (exterior case)
[0069] 5 winding stopper tape [0070] 6 capacitor element [0071] 7
cathode foil [0072] 8 anode foil [0073] 9 electrolytic paper
(separator) [0074] 11 terminal [0075] 20 pressure valve [0076] 21
recessed part [0077] 22 first inclined surface [0078] 23 second
inclined surface [0079] 24 flat part [0080] 31 groove part [0081]
P1, P2 inflection point
* * * * *